I. Field of the Invention
This invention relates generally to methods and compositions for constructing insulating glass units and in particular, methods and compositions for making a desiccant matrix which is applied to a metal spacer assembly used in the construction of insulating glass units. Most specifically, the present invention relates to a powdered desiccant which is suspended in an atmospheric curing resin, the resin being in a liquid phase at room temperature.
II. Description of the Prior Art
Insulating glass units generally comprise a pair of glass sheets maintained in a spaced apart relationship to each other by a spacing and sealing assembly which extends around the periphery of the inner, facing surfaces of the glass sheets, to define a sealed and insulating air space between the glass sheets. A spacer assembly generally comprises an inner spacer-dehydrator element which extends around the periphery of the inside facing surfaces of the glass sheets. The inner surfaces of the glass sheets are attached to the outer surface of the spacer assembly by means of a sealant or adhesive.
In one typical form of insulating glass unit, the inner spacer-dehydrator element comprises a hollow metal spacer element generally adhered to the periphery of the inside, facing surfaces of the sheets, to provide an insulating air space. The metal spacer element is generally tubular in shape and filled with a desiccant material, which is put in communication with the insulating air space to absorb moisture therefrom, and to enhance the performance and durability of the unit. The desiccant prevents moisture condensation on the inner surfaces of the window panes.
There are several known ways of filling the spacer assembly with the desiccant material. One known way is to manually pour beads which serve as carriers for the desiccant in the spacer assembly. This method is unsatisfactory because it is both inefficient and labor intensive. Another approach to applying the desiccant material to the spacer assembly is to utilize a powdered molecular desiccant which is carried in a hot melt butyl thermoplastic carrier. There are numerous problems with this approach. Because the hot melt carrier must be maintained at an elevated temperature while the desiccant material is being applied to the spacer, this procedure requires elevated temperature application equipment, thereby increasing initial capital costs and operating costs. Additionally, since the desiccant impregnated spacers often times must be handled right after application of the desiccant material, the hot melt systems increase the likelihood that operators of the equipment as well as handlers of the spacers will get burned. Finally, the use of thermoplastic materials to carry the powdered desiccant may compromise the aesthetic integrity of the insulating glass unit in that even after installation, the desiccant carrier can remelt and/or sag if the window unit is exposed to elevated temperatures. This makes the use of thermoplastics as desiccant carriers highly undesirable for window units installed in locations having hot climates.
U.S. Pat. No. 4,622,249 discloses a silicone glazing adhesive/sealant as a desiccant carrier. The carrier material is a flexible, organic, room temperature vulcanizable adhesive sealant material comprised of two components. One of the components comprises a base material and the other component comprises a curing agent or accelerator. Neither of the components is individually curable or vulcanizable. When the two components are combined, a chemical cross linking reaction takes place which begins curing or vulcanizing the two-component material at room temperature.
U.S. Pat. No. 3,758,996 discloses a desiccant material which is carried in a thermoplastic carrier. In one example, the desiccant matrix is applied to the spacer assembly at a temperature above 250.degree. F.
The present invention overcomes all of the problems of the prior art in that it provides a desiccant matrix for use in a spacer assembly of an insulating glass unit which can be applied as a single component and at room temperature. Upon exposure to the atmosphere, the desiccant matrix irreversibly cures into a solid structure, thereby preventing the desiccant from running or sagging at some later date after installation of the window unit. Since the desiccant matrix can be applied as a single component and at room temperature, operating costs are kept down, as well as minimizing the potential risk of injury to workers who must handle the spacer assemblies. These and other advantages of the present invention will be readily apparent from the description, the discussion and examples which follow.